Intracellular signal transduction of parathyroid hormone receptor activation and its pathphysiology

1. 为了推断狗甲状旁腺激素（PTH）受体的氨基酸序列，利用狗肝脏和肾脏的cDNA文库进行cDNA克隆。结果表明，犬甲状旁腺激素受体是具有7个跨膜结构域的G蛋白偶联膜蛋白，且犬甲状旁腺激素受体的氨基酸序列与人（95.3%）、大鼠（88.0%）和负鼠（79.1%）具有同源性。northern blot分析显示PTH受体在肾、肝、脑、主动脉和骨髓中均有表达。2. 在大鼠肠系膜上动脉中检测PTH对细胞内Ca^<2+> ([Ca^<2+>] in)收缩和变化的影响，了解PTH受体激活的细胞内信号转导。PTH对phenyphrine诱导的[Ca^<2+>]的收缩和增加的抑制作用大于高浓度KCI（高K）。PTH抑制ip3诱导的苯甲肾上腺素激活的Ca^<2+>释放，而对咖啡因激活的Ca^<2+>诱导的Ca^<2+>释放无影响。PTH降低了高钾引起的收缩，但对[Ca^<2+>] in的变化无抑制作用，提示PTH对收缩机制有直接抑制作用。PTH受体的细胞内信号转导可能通过腺苷酸环化酶的激活与环AMP的增加相结合。3. 研究了ip3诱导Ca^<2+>释放的特性和Ca^<2+>被吸收到Ca^<2+>库中的来源。Ca^<2+>的释放不仅激活了收缩机制，还激活了Ca^<2+>激活的K^+通道。Ca^<2+>存储似乎优先通过唯一的Ca^<2+>通道，而不是电压依赖的Ca^<2+>通道，进入Ca^<2+>。甲状旁腺素可能通过循环amp依赖途径影响Ca^<2+>的释放和/或Ca^<2+>的摄取。

1. In order to deduce the amino acid sequence of dog parathyroid hormone (PTH) receptors, cDNA cloning was carried out using the cDNA library of the liver and kidney. We found that dog PTH receptors were putative G protein-coupled membrane protein having seven membrane spanning domains and that the amino acid sequence of PTH receptors of the dog was homologus that of human (95.3%), rat (88.0%) or opossum (79.1%). The northern blot analysis showed that PTH receptors were expressed in the kidney, liver, brain, aorta and bone marrow. 2. The effect of PTH on contractions and changes in intracellular Ca^<2+> ( [Ca^<2+>] in) was examined in the rat superior mesenteric artery to know the intracellular signal transduction of the PTH receptor activation. PTH inhibited a contraction and increase in [Ca^<2+>] in induced by phenyrephrine greater than that by high concentrations of KCI (high K). PTH inhibited IP3-induced Ca^<2+> release actibated by phenyrephrine without any effects on Ca^<2+>-induced Ca^<2+> release activated by caffeine. PTH decreased a contraction evoked by high K without inhibitory effects on changes in [Ca^<2+>] in, suggesting that PTH has a direct inhibitory effect on the contractile machinery. Intracellular signal trasduction by the PTH receptor may be coupled with increases in cyclic AMP by the activation of the adenylate cyclase. 3. The characteristics of IP3-induced Ca^<2+> release and the source of Ca^<2+> taken up into Ca^<2+> stores were examined in the intestinal smooth muscle. Ca^<2+> released from the store activated not only the contractile machinery but also Ca^<2+>-activated K^+ channels. Ca^<2+> stores seem to take up into Ca^<2+> preferentially passing through unique Ca^<2+> channels, but not voltage-dependent Ca^<2+> channels. PTH may affect the Ca^<2+> release and/or Ca^<2+> uptake through cyclic AMP-dependent pathways.